In recent years, a variety of projectors have been widely used in various video applications. For example, projectors can be used for making presentations, holding meetings or giving lectures in classrooms, boardrooms, conference rooms or home theaters. By the projector, an image signal from an image signal source can be enlarged and shown on a projection screen. For reducing power loss and overall volume and increasing the image quality, the illumination system of the current projector employs a solid-state light-emitting element (e.g. light emitting diode or laser diode) to replace the conventional high intensity discharge (HID) lamp or ultra-high pressure (UHP) mercury lamp.
Generally, for increasing the total light amount, plural solid-state light-emitting elements of the conventional illumination system are arranged in an array. Moreover, plural reflective mirrors are aligned with the optical axis of the array of the solid-state light-emitting elements. The light beams from the array of the solid-state light-emitting elements are reflected by the reflective mirrors and guided to the same focusing lens. After the light beams are focused by the focusing lens, the focused light beams are guided to an imaging system.
However, due to the assembly tolerance of the light-emitting elements and the reflective mirrors or the characteristics of the light-emitting elements (e.g. the beam angle), the light beams reflected by the reflective mirrors cannot be effectively centralized and guided to the same focusing lens. Moreover, since no proper adjusting mechanism can be used to adjust the reflective mirrors, the above drawbacks fail to be overcome. Under this circumstance, the power loss is increased, and the utilization efficiency of the illumination system is deteriorated. Moreover, since the intensity of the light beams introduced into the projection device is insufficient, the image quality and the luminance are adversely affected. Since the reflected light beams are not propagated along the specified optical path, the temperature of the illumination system is increased.
Therefore, there is a need of providing an improved illumination system in order to overcome the above drawbacks.